Upregulates Caveolin-1 Expression Research Articles

Zedoarondiol inhibits human bronchial smooth muscle cell proliferation through the CAV-1/PDGF signalling pathway

Airway remodelling in lung diseases can be treated by inhibiting excessive smooth muscle cell proliferation. Zedoarondiol (Zed) is a natural compound isolated from the Chinese herb Curcuma longa. The caveolin-1 (CAV-1) is widely expressed in lung cells and plays a key role in platelet-derived growth factor (PDGF) signalling and cell proliferation. This study aims to investigate the effect of Zed on human bronchial smooth muscle cell (HBSMC) proliferation and explore its potential molecular mechanisms. We assessed the effect of Zed on the proliferation of PDGF-stimulated HBSMCs and performed proteomic analysis to identify potential molecular targets and pathways. CAV1 siRNA was used to validate our findings in vitro. In PDGF-stimulated HBSMCs, Zed significantly inhibited excessive proliferation of HBSMCs. Proteomic analysis of zedoarondiol-treated HBSMCs revealed significant enrichment of differentially expressed proteins in cell proliferation-related pathways and biological processes. Zed inhibition of HBSMC proliferation was associated with upregulation of CAV1, regulation of the CAV-1/PDGF pathway and inhibition of MAPK and PI3K/AKT signalling pathway activation. Treatment of HBSMCs with CAV1 siRNA partly reversed the inhibitory effect of Zed on HBSMC proliferation. Thus, this study reveals that zedoarondiol potently inhibits HBSMC proliferation by upregulating CAV-1 expression, highlighting its potential value in airway remodelling and related diseases.

Endothelial β-Catenin Deficiency Causes Blood-Brain Barrier Breakdown via Enhancing the Paracellular and Transcellular Permeability.

Disruption of the blood-brain barrier (BBB) causes or contributes to neuronal dysfunction and several central nervous system (CNS) disorders. Wnt/β-catenin signaling is essential for maintaining the integrity of the adult BBB in physiological and pathological conditions, including stroke. However, how the impairment of the endothelial Wnt/β-catenin signaling results in BBB breakdown remains unclear. Furthermore, the individual contributions of different BBB permeability-inducing mechanisms, including intercellular junction damage, endothelial transcytosis, and fenestration, remains unexplored. Here, we induced β-catenin endothelial-specific conditional knockout (ECKO) in adult mice and determined its impact on BBB permeability and the underlying mechanism. β-catenin ECKO reduced the levels of active β-catenin and the mRNA levels of Wnt target genes in mice, indicating downregulation of endothelial Wnt/β-catenin signaling. β-catenin ECKO mice displayed severe and widespread leakage of plasma IgG and albumin into the cerebral cortex, which was absent in wild-type controls. Mechanistically, both the paracellular and transcellular transport routes were disrupted in β-catenin ECKO mice. First, β-catenin ECKO reduced the tight junction protein levels and disrupted the intercellular junction ultrastructure in the brain endothelium. Second, β-catenin ECKO substantially increased the number of endothelial vesicles and caveolae-mediated transcytosis through downregulating Mfsd2a and upregulating caveolin-1 expression. Interestingly, fenestration and upregulated expression of the fenestration marker Plvap were not observed in β-catenin ECKO mice. Overall, our study reveals that endothelial Wnt/β-catenin signaling maintains adult BBB integrity via regulating the paracellular as well as transcellular permeability. These findings may have broad applications in understanding and treatment of CNS disorders involving BBB disruption.

Caveolin-1 Regulation and Function in Mouse Uterus during Early Pregnancy and under Human In Vitro Decidualization.

Decidualization is essential to rodent and primate pregnancy. Senescence is increased during decidualization. Failure of senescence clearance during decidualization will cause pregnancy abnormality. Caveolin-1 is located in plasmalemmal caveolae and involved in senescence. However, whether caveolin-1 is involved in decidualization remains undefined. In this study, we examined the expression, regulation and function of Caveolin-1 during mouse early pregnancy and under mouse and human in vitro decidualization. From days 1 to 8 of pregnancy, Caveolin-1 signals are mainly located in endothelium and myometrium. Estrogen stimulates Caveolin-1 expression in endothelium. Deficiency of estrogen receptor α significantly promotes Caveolin-1 level in uterine stromal cells. Progesterone upregulates Caveolin-1 expression in luminal epithelium. During mouse in vitro decidualization, Caveolin-1 is significantly increased. However, Caveolin-1 is obviously decreased during human in vitro decidualization. Caveolin-1 overexpression and siRNA suppress and upregulate IGFBP1 expression under in vitro decidualization, respectively. Blastocysts-derived tumor necrosis factor α (TNFα) and human Chorionic Gonadotropin (hCG) regulate Caveolin-1 in mouse and human decidual cells, respectively. Caveolin-1 levels are also regulated by high glucose and insulin. In conclusion, a low level of Caveolin-1 should be beneficial for human decidualization.

TLR4-Myd88 pathway upregulated caveolin-1 expression contributes to coronary artery spasm

AimTo study the role of toll-like receptors 4-myeloid differentiation factor 88 (TLR4-Myd88) dependent caveolin-1 (Cav-1) expression modulation in coronary artery spasm (CAS) and explore the underlying pathogenic mechanisms. Methods and resultsLipopolysaccharide (LPS) and acetylcholine (Ach) were used to develop the in vitro and in vivo models mimicking the physiological CAS microenvironment. LPS-induced upregulation of Cav-1 expression in mouse coronary and aorta endothelial cells was shown by western blot and immunofluorescence (IF) staining (p < 0.01). Caveolin-1-knockout (Cav-1−/−) mice had reduced aortic inflammation after LPS challenge, and fewer ST segment changes were observed through electrocardiogram (ECG) monitoring compared to wild type mice after LPS and ACh administration. In vitro, pretreating human umbilical vein endothelial cells (HUVECs) with siCav-1 to knock down Cav-1 expression reduced the endothelial inflammation following LPS challenge. SiCav-1 also partially reversed the attenuated Ca2+ concentration after LPS and ACh administration compared to the control group, which was evaluated by fluorescent molecular probing for Ca2+ alternation monitoring (p < 0.05). TLR4 and Myd88 downregulation by siRNA partially blocked the increased Cav-1 mRNA and protein expressions following LPS treatment, as well as partially reversed the decreased NO production evaluated by nitrate reductase method and the impaired Ca2+ concentration of endothelial cells induced by LPS and ACh. ConclusionThese findings suggested that Cav-1, which was upregulated by TLR4-Myd88, served as an important modulator of CAS microenvironment establishment in vivo and in vitro, making it a potential pharmacologic target for the treatment of vasospasm via reduced endothelial cell inflammation.

Cystatin C improves blood-brain barrier integrity after ischemic brain injury in mice.

Cystatin C, a well-established biomarker of renal function, has been associated with a protective effect against stroke. However, the potential neuroprotective mechanism of cystatin C in ischemic brain injury remains unclear. Our study hypothesized that cystatin C can ameliorate blood-brain barrier (BBB) disruption by up-regulating caveolin-1 expression, thereby improving neurological outcomes in cerebral ischemic injury. Western blotting, immunohistochemistry, immunofluorescence staining, and immunoprecipitation were performed to investigate target proteins. Evans Blue and gelatin zymography were used to examine the effect of cystatin C on BBB disruption. Plasmid and small interfering RNA transfection was used to observe alterations in caveolin-1 and occludin expression induced by changes in cystatin C expression. Intriguingly, our study showed that the expression of both cystatin C and caveolin-1 was increased in middle cerebral artery occlusion-injured mice, and pretreatment with exogenous cystatin C significantly increased caveolin-1 expression, reduced Evans Blue leakage in the injured brain region, and decreased the enzymatic activity of matrix metallopeptidase-9. Meanwhile, our study also showed that the over-expression of cystatin C greatly enhanced caveolin-1 expression, which later increased occludin expression in oxygen-glucose deprivation-exposed brain microvascular endothelial cells. The knockdown of cystatin C induced the opposite outcomes. These experimental results indicate a positive role for cystatin C in the regulation of caveolin-1 and occludin expression in cerebral ischemic injury. Taken together, these data unveil a new mechanism of the regulation of caveolin-1 expression by cystatin C in the maintenance of BBB integrity after ischemic brain injury and provide new clues for the identification of potential therapeutic strategies for stroke.

Maternal chronic intermittent hypoxia in rats causes early atherosclerosis with increased expression of Caveolin-1 in offspring.

The objective of our research was to explore the effects of maternal and postpartum chronic intermittent hypoxia (CIH) exposure on atherosclerosis in adulthood offspring of rats, and the role of Caveolin-1 in the course. Sixteen rats were assigned to two groups (n = 8), maternal normoxia and CIH group. After delivery, two male pups per litter were selected and breastfed for 1month, which then randomly received postpartum normoxia or CIH. Thus, 4 groups were created as follows (n = 8): (1) maternal normoxia and postpartum normoxia group, (2) maternal CIH and postpartum normoxia group, (3) maternal CIH and postpartum CIH group, and (4) maternal normoxia and postpartum CIH group. The offspring were weighed at birth and weaning. After the duration of 12-week experiment, morphological changes, the expression of Caveolin-1 and NF-κB p65 in the aorta were detected. Maternal CIH resulted in significantly lower body weight and thicker intima (P < 0.001). CIH upregulated the expression of Caveolin-1 and NF-κB p65 significantly (P < 0.01). There was a synergistic effect of maternal and postpartum CIH on the thickening of intima (P < 0.05), also on the expression of Caveolin-1 and NF-κB p65 (P < 0.01). The results demonstrate that maternal CIH exposure causes a postpartum catch-up growth and early atherosclerotic changes followed by upregulating Caveolin-1 expression. Besides, maternal CIH enhances the atherosclerotic changes caused by postpartum CIH. Oxidative stress probably implicates in above effects.

Intermittent hypoxia regulates vasoactive molecules and alters insulin-signaling in vascular endothelial cells

Vascular dysfunction and insulin resistance (IR) are associated with obstructive sleep apnea (OSA), which is characterized by frequent episodes of nocturnal intermittent hypoxia (IH). While it is recognized that the balance between vasoconstrictive (endothelin-1) and vasodilatory molecules (nitric oxide, NO) determine vascular profile, molecular mechanisms contributing to vascular dysfunction and IR in OSA are not completely understood. Caveolin-1 is a membrane protein which regulates endothelial nitric oxide synthase (eNOS) activity which is responsible for NO generation and cellular insulin-signaling. Hence, we examined the effects of IH on caveolin-1, eNOS, and endothelin-1 in human coronary artery endothelial cells in the context of IR. Chronic 3-day IH exposure up-regulated caveolin-1 and endothelin-1 expression while reducing NO. Also, IH altered insulin-mediated activation of AKT but not ERK resulting in increased endothelin-1 transcription. Similarly, caveolin-1 overexpression attenuated basal and insulin-stimulated NO synthesis along with impaired insulin-dependent activation of AKT and eNOS, with no effect on insulin-stimulated ERK1/2 phosphorylation and endothelin-1 transcription. Our data suggest that IH contributes to a vasoconstrictive profile and to pathway-selective vascular IR, whereby insulin potentiates ET-1 expression. Moreover, IH may partly mediate its effects on NO and insulin-signaling via upregulating caveolin-1 expression.

An Rb family–independent E2F3 transcription factor variant impairs STAT5 signaling and mammary gland remodeling during pregnancy in mice

E2F transcription factors are regulated by binding to the retinoblastoma (Rb) tumor suppressor family of proteins. Previously, we reported an E2FLQ mutation that disrupts the binding with Rb proteins without affecting the transcriptional activity of E2F. We also showed that mouse embryonic fibroblasts with an E2F3LQ mutation exhibit increased E2F activity and more rapid cell proliferation. In this report, we analyzed E2F3LQ mice to further characterize the in vivo consequences of Rb family-independent E2F3 activity. We found that homozygous E2F3LQ mice were viable and had no obvious developmental defects or tumor growth. Our results also indicated that E2F3LQ cells largely retain normal control of cell proliferation in vivo However, female E2F3LQ mice had partial nursing defects. Examination of the E2F3LQ mammary glands revealed increased caveolin-1 (CAV1) expression, reduced prolactin receptor/Stat5 signaling, and impaired pregnancy-induced cell proliferation and differentiation. Of note, ChIP experiments disclosed that E2F3 binds the CAV1 promoter. Furthermore, E2F3 overexpression induced CAV1 expression, and CRISPR/CAS9-mediated E2F3 knockout reduced CAV1 levels and also increased prolactin receptor-induced Stat5 signaling in mammary epithelial cells. Our results suggest that the Rb family-independent E2F3 LQ variant inhibits pregnancy-induced mammary gland cell proliferation and differentiation by up-regulating CAV1 expression and inhibiting Stat5 signaling.

Abstract 4308: Cordycepin induces apoptosis by caveolin-1-mediated JNK regulation of Foxo3a in human lung adenocarcinoma cells

Abstract Forkhead transcription factor (Foxo3a) is a critical effector of JNK-mediated tumor suppression. However, it is not clear whether the caveolin-1 (CAV1)-mediated JNK/Foxo3a pathway is involved in cancer cell apoptosis. We found that cordycepin upregulates CAV1 expression, which was accompanied by JNK phosphorylation (p-JNK), and, subsequently Foxo3a translocation into the nucleus, resulting in the upregulation of Bax protein expression. Furthermore, we found that CAV1 overexpression upregulated p-JNK whereas CAV1 siRNA downregulated p-JNK. Additionally, SP600125, a specific JNK inhibitor, significantly increased Foxo3a phosphorylation, which attenuated Foxo3a translocation into the nucleus, indicating that CAV1 mediates JNK regulation of Foxo3a. Foxo3a siRNA downregulated Bax protein and attenuated A549 apoptosis, indicating that the CAV1-mediated JNK/Foxo3a pathway induces the apoptosis of A549 lung cancer cells. Cordycepin significantly decreased tumor volume in nude mice. Taken together, these results indicate that cordycepin promotes CAV1 upregulation to enhance JNK/Foxo3a signaling pathway activation inducing apoptosis in lung cancer cells and support its potential as a therapeutic agent for lung cancer. Citation Format: Eunbi Jo, Hyun Jin Jang, Ik-Soon Jang. Cordycepin induces apoptosis by caveolin-1-mediated JNK regulation of Foxo3a in human lung adenocarcinoma cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4308. doi:10.1158/1538-7445.AM2017-4308

Cordycepin induces apoptosis by caveolin-1-mediated JNK regulation of Foxo3a in human lung adenocarcinoma

Forkhead transcription factor (Foxo3a) is a downstream effector of JNK-induced tumor suppression. However, it is not clear whether the caveolin-1 (CAV1)-mediated JNK/Foxo3a pathway is involved in cancer cell apoptosis. We found that cordycepin upregulates CAV1 expression, which was accompanied by JNK phosphorylation (p-JNK) and subsequent Foxo3a translocation into the nucleus, resulting in the upregulation of Bax protein expression. Furthermore, we found that CAV1 overexpression upregulated p-JNK, whereas CAV1 siRNA downregulated p-JNK. Additionally, SP600125, a specific JNK inhibitor, significantly increased Foxo3a phosphorylation, which downregulated Foxo3a translocation into the nucleus, indicating that CAV1 mediates JNK regulation of Foxo3a. Foxo3a siRNA downregulated Bax protein and attenuated A549 apoptosis, indicating that the CAV1-mediated JNK/Foxo3a pathway induces the apoptosis of A549 lung cancer cells. Cordycepin significantly decreased tumor volume in nude mice. Taken together, these results indicate that cordycepin promotes CAV1 upregulation to enhance JNK/Foxo3a signaling pathway activation, inducing apoptosis in lung cancer cells, and support its potential as a therapeutic agent for lung cancer.

Inflammatory cytokines induce caveolin-1/β-catenin signalling in rat nucleus pulposus cell apoptosis through the p38 MAPK pathway.

Apoptosis of nucleus pulposus (NP) cells is a major cause of intervertebral disc degeneration. To elucidate relationships between caveolin-1 and cytokine-induced apoptosis, we investigated the role of caveolin-1 in cytokine-induced apoptosis in rat NP cells and the related signalling pathway. Rat NP cells were treated with interleukin (IL)-1β or tumour necrosis factor alpha (TNF-α), and knockdown of caveolin-1 and β-catenin was achieved using specific siRNAs. Then, apoptotic level of rat NP cells and expression and activation of caveolin-1/β-catenin signalling were assessed by flow cytometric analysis, qRT-PCR, western blotting and luciferase assays. The relationship between the mitogen-activated protein kinase (MAPK) pathway and caveolin-1 promoter activity was also determined by luciferase assays. IL-1β and TNF-α induced apoptosis, upregulated caveolin-1 expression and activated Wnt/β-catenin signalling in rat NP cells, while the induction effect of cytokines was reversed by caveolin-1 siRNA and β-catenin siRNA. Promotion of rat NP cell apoptosis and nuclear translocation of β-catenin induced by caveolin-1 overexpression were abolished by β-catenin siRNA. Furthermore, pretreatment with a p38 MAPK inhibitor or dominant negative-p38, blocked cytokine-dependent induction of caveolin-1/β-catenin expression and activity. The results revealed the role of p38/caveolin-1/β-catenin in inflammatory cytokine-induced apoptosis in rat NP cells. Thus, controlling p38/caveolin-1/β-catenin activity seemed to regulate IL-1β- and TNF-α-induced apoptosis in the NP during intervertebral disc degeneration.

Tissue damage negatively regulates LPS-induced macrophage necroptosis.

Infection is a common clinical complication following tissue damage resulting from surgery and severe trauma. Studies have suggested that cell pre-activation by antecedent trauma/tissue damage profoundly impacts the response of innate immune cells to a secondary infectious stimulus. Cell necroptosis, a form of regulated inflammatory cell death, is one of the mechanisms that control cell release of inflammatory mediators from important innate immune executive cells such as macrophages (Mφ), which critically regulate the progress of inflammation. In this study, we investigated the mechanism and role of trauma/tissue damage in the regulation of LPS-induced Mφ necroptosis using a mouse model simulating long-bone fracture. We demonstrate that LPS acting through Toll-like receptor (TLR) 4 promotes Mφ necroptosis. However, necroptosis is ameliorated by high-mobility group box 1 (HMGB1) release from damaged tissue. We show that HMGB1 acting through cell surface receptor for advanced glycation end products (RAGE) upregulates caveolin-1 expression, which in turn induces caveolae-mediated TLR4 internalization and desensitization to decrease Mφ necroptosis. We further show that RAGE-MyD88 activation of Cdc42 and subsequent activation of transcription factor Sp1 serves as a mechanism underlying caveolin-1 transcriptional upregulation. These results reveal a previous unidentified protective role of damage-associated molecular pattern (DAMP) molecules in restricting inflammation in response to exogenous pathogen-associated molecular pattern molecules.

Effect of quercetin and its metabolite on caveolin-1 expression induced by oxidized LDL and lysophosphatidylcholine in endothelial cells.

Oxidized low-density lipoprotein contributes to atherosclerotic plaque formation, and quercetin is expected to exert anti-atherosclerotic effects. We previously reported accumulation of conjugated quercetin metabolites in the aorta of rabbits fed high-cholesterol diets with quercetin glucosides, resulting in attenuation of lipid peroxidation and inhibition of lipid accumulation. Caveolin-1, a major structural protein of caveolae in vascular endothelial cells, plays a role in atherosclerosis development. Here we investigated effects of oxidized low-density lipoprotein, quercetin and its metabolite, quercetin 3-O-β-glucuronide, on caveolin-1 expression. Oxidized low-density lipoprotein significantly upregulated caveolin-1 mRNA expression. An oxidized low-density lipoprotein component, lysophosphatidylcholine, also induced expression of both caveolin-1 mRNA and protein. However, lysophosphatidylcholine did not affect the location of caveolin-1 proteins within caveolae structures. Co-treatment with quercetin or quercetin 3-O-β-glucuronide inhibited lysophosphatidylcholine-induced caveolin-1 expression. Quercetin and quercetin 3-O-β-glucuronide also suppressed expression of adhesion molecules induced by oxidized low-density lipoprotein and lysophosphatidylcholine. These results strongly suggest lysophosphatidylcholine derived from oxidized low-density lipoprotein contributes to atherosclerotic events by upregulating caveolin-1 expression, resulting in induction of adhesion molecules. Quercetin metabolites are likely to exert an anti-atherosclerotic effect by attenuating caveolin-1 expression in endothelial cells.

Rosiglitazone ameliorates diffuse axonal injury by reducing loss of tau and up-regulating caveolin-1 expression.

Rosiglitazone up-regulates caveolin-1 levels and has neuroprotective effects in both chronic and acute brain injury. Therefore, we postulated that rosiglitazone may ameliorate diffuse axonal injury via its ability to up-regulate caveolin-1, inhibit expression of amyloid-beta precursor protein, and reduce the loss and abnormal phosphorylation of tau. In the present study, intraperitoneal injection of rosiglitazone significantly reduced the levels of amyloid-beta precursor protein and hyperphosphorylated tau (phosphorylated at Ser(404)(p-tau (S(404))), and it increased the expression of total tau and caveolin-1 in the rat cortex. Our results show that rosiglitazone inhibits the expression of amyloid-beta precursor protein and lowers p-tau (S(404)) levels, and it reduces the loss of total tau, possibly by up-regulating caveolin-1. These actions of rosiglitazone may underlie its neuroprotective effects in the treatment of diffuse axonal injury.

Changes of caveolin-1 in the livers of mice with nonalcoholic fatty liver disease caused by high-fat diet

Objective To explore the role of caveolin-1 in nonalcoholic fatty liver disease (NAFLD) caused by high-fat diet.Methods A total of 12 ten-week-old male C57BL/6 mice were fed with high-fat and high-cholesterol diet for 14 weeks to establish the NAFLD animal model.And six syngeneic mice fed with normal diet at the same time were taken as control.All the mice were sacrificed by the end of 14th week,body weight,liver weight and the changes of serum lipids of the two groups were compared.The changes of caveolin-1 at mRNA and protein levels in the liver of mice with NAFLD were detected by quantitative polymerase chain reaction (qPCR) and Western blot.The liver steatosis of the mice was observed under light microscopy after stained by hematoxylin and eosin.The changes of distribution of caveolin-1 in liver were examined by immunohistochemistry.The differences of caveolin-1 at mRNA and protein level in livers between the two groups were compared by t test.The differences of immunohistochemical scores of caveolin-1 expression in the livers of mice with different degree of fatty liver were analyzed by ordinal variables of two independent samples ranksum test analysis.Results After 14 weeks high-fat and high-cholesterol diet,all the mice of experiment group developed NAFLD.Nine of which were severe and three were moderate.Compared with the control group,serum total cholesterol,high density lipoprotein cholesterol and low density lipoprotein cholesterol of experiment group significantly increased ((1.940 ± 0.300) mmol/L vs (3.771±0.800) mmol/L,(1.120±0.066) mmol/L vs (2.224±0.420) mmol/L,(0.510±0.191) mmol/L vs (1.241±0.660) mmol/L,t=-3.760,-5.474,-3.332,all P＜0.01),however there was no significant difference in triglyceride (P＞0.05).The caveolin-1 of experiment group significantly increased at mRNA (1.536 ±0.226 vs 0.980± 0.272,t=3.371,P＜0.05) and protein levels (0.643±0.240 vs 0.100±0.130,t=4.847,P＜0.01).The immunohistochemical results indicated that the increased caveolin-1 expression mainly distributed in the membrane of hepatocytes,cytoplasm and membrane of lipid droplets.Conclusion The up-regulated caveolin-1 expression in the livers of NAFLD mice induced by high-fat and high-cholesterol may be involved in the mechanism of NAFLD. Key words: Caveolin 1 ; Fatty liver; Hyperlipidemias; Cholesterol, dietary; Mice, inbred C57BL

Response of chondrocytes to shear stress: antagonistic effects of the binding partners Toll‐like receptor 4 and caveolin‐1

Osteoarthritis (OA) is often a consequence of excessive mechanical loading of cartilage, which produces hydrostatic stress, tensile strain, and fluid flow. Application of high fluid shear to chondrocytes recapitulates the earmarks of OA, as evidenced by the induction of cyclooxygenase-2, prostaglandins (PGs), and interleukin-6 (IL-6). Here, we delineated the signaling pathway by which high fluid shear mediates the temporal regulation of IL-6 synthesis in human chondrocytes. We determined that Toll-like receptor 4 (TLR4) and caveolin-1 are binding partners in chondrocytes. Their expression is temporally regulated by fluid shear via the sequential up-regulation of microsomal PGE synthase-1 (mPGES-1) and L-PGDS. High shear stress rapidly induces an 8-fold up-regulation of TLR4 expression via an mPGES-1-dependent pathway, whereas prolonged shear exposure concurrently down-regulates TLR4 by >4-fold and up-regulates caveolin-1 expression by > 2.5-fold in an L-PGDS-dependent manner. TLR4 and caveolin-1 exert opposing effects on the activation of ERK1/2, PI3-K and PKA signaling pathways, which, in turn, regulate the NF-κB-dependent IL-6 synthesis in a time-dependent fashion. Reconstructing the signaling network regulating shear-induced IL-6 expression in chondrocytes may provide insights for developing therapeutic strategies to combat osteoarthritis.

Transcriptional Repression of Caveolin-1 (CAV1) Gene Expression by GATA-6 in Bladder Smooth Muscle Hypertrophy in Mice and Human Beings

Hypertrophy occurs in urinary bladder wall smooth muscle (BSM) in men with partial bladder outlet obstruction (PBOO) caused by benign prostatic hyperplasia (BPH) and in animal models of PBOO. Hypertrophied BSM from the rabbit model exhibits down-regulation of caveolin-1, a structural and functional protein of caveolae that function as signaling platforms to mediate interaction between receptor proteins and adaptor and effector molecules to regulate signal generation, amplification, and diversification. Caveolin-1 expression is diminished in PBOO-induced BSM hypertrophy in mice and in men with BPH. The proximal promoter of the human and mouse caveolin-1 (CAV1) gene was characterized, and it was observed that the transcription factor GATA-6 binds this promoter, causing reduced expression of caveolin-1. Furthermore, caveolin-1 expression levels inversely correlate with the abundance of GATA-6 in BSM hypertrophy in mice and human beings. Silencing of GATA6 gene expression up-regulates caveolin-1 expression, whereas overexpression of GATA-6 protein sustains the transcriptional repression of caveolin-1 in bladder smooth muscle cells. Together, these data suggest that GATA-6 acts as a transcriptional repressor of CAV1 gene expression in PBOO-induced BSM hypertrophy in men and mice. GATA-6-induced transcriptional repression represents a new regulatory mechanism of CAV1 gene expression in pathologic BSM, and may serve as a target for new therapy for BPH-induced bladder dysfunction in aging men.

Transcriptional Repression of Caveolin-1 gene Expression by Gata-6 in Bladder Smooth Muscle Hypertrophy in Mice and Humans

Caveolin-1 is a structural and functional protein of caveolae that function as signaling platforms to mediate interaction between receptor proteins and adaptor and effector molecules to regulate signal generation, amplification, and diversification. Hypertrophied bladder smooth muscle (BSM) from the rabbit model of partial bladder outlet obstruction (PBOO) and men with benign prostatic hyperplasia (BPH)-induced PBOO shows a downregulation of Caveolin-1 and caveolar structural alteration. Here we report that caveolin-1 expression is diminished in PBOO-induced BSM hypertrophy in mice and in men with BPH. We characterized the proximal promoterof the human and mouse caveolin-1 gene and found that the transcriptionfactor GATA-6 binds this promoter, causing reduced expression of caveolin-1. Furthermore, we demonstrate that caveolin-1 expression levels inversely correlate with the abundance of GATA-6 in BSM hypertrophy in mice and humans. Importantly, silencing of GATA-6 gene expression up-regulates caveolin-1 expression, whereas overexpression of GATA-6 protein sustains the transcriptional repression of caveolin-1 in BSM cells. Together, our data suggest that GATA-6 acts as a transcriptional repressor of caveolin-1 gene expression in PBOO-induced BSM hypertrophy in men and mice. The GATA-6-induced transcriptional repression represents a new regulatory mechanism for caveolin-1 gene expression in pathologic BSM. Regulating the GATA-6 transcriptional regulation may serve as a target for new therapy for BPH-induced bladder dysfunction in aging men. Supported by O’Brien Urology Center Grant P50 DK052620

Leptin upregulates caveolin-1 expression: Implications for development of atherosclerosis

Objective To determine the role of hyperleptinemia on caveolin-1 expression and leptin signaling. Methods Endothelial cells are critical to atherosclerosis development; therefore we investigated hyperleptinemia in cultured vascular endothelial cells. Dose-dependent effect of leptin on caveolin-1 expression was determined by Western blot analysis. Also, the consequence of increased caveolin-1 expression on leptin signaling was investigated by adenovirus mediated caveolin-1 overexpression. The effect of increased caveolin-1 expression on leptin-dependent activation of ERK1/2 and eNOS was determined by Western blot analysis. Results Leptin upregulates caveolin-1 protein expression in a dose dependent manner and increased caveolin-1 expression impairs leptin signaling. Conclusions Leptin increases caveolin-1 protein expression which impairs leptin signaling in vascular endothelial cells. Our study identifies an additional leptin mediated proatherogenic mechanism and a novel caveolin-1 dependent leptin feedback mechanism which may have implications for development of peripheral leptin resistance in the endothelium.

Daxx Mediates Oxidized Low-density Lipoprotein-Induced Cholesterol Accumulation and Apoptosis in Macrophages by Upregulating Caveolin-1 Expression*

Daxx Mediates Oxidized Low-density Lipoprotein-Induced Cholesterol Accumulation and Apoptosis in Macrophages by Upregulating Caveolin-1 Expression*